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                [Cerc2012]Word equations                </h1>
                <p>时间限制：40s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><p>给定一篇文章T和一个单词P，你希望知道是否可以通过从T中删除一些字母得到P。比如，单词programming可以得到pong或者program或者roaming，但是得不到map。保证所有单词只包含英文小写字母。</p>
<div>然而文章T通过一种等价形式进行了加密。等式使用一些特殊的符号（由大写字母组成），每个符号都用来表示一个由小写字母组成的单词。每个等式都满足下面之一的形式：</div>
<div>A = 由小写字母组成的单词</div>
<div>或</div>
<div>A = B + C</div>
<div>其中A, B, C可以表示任何特殊的符号，而 + 号表示单词的拼接。这种等价形式是：</div>
<div>明确的&mdash;&mdash;对于每个固定的符号A，只有一个A在等式的左边（A在左边只出现一次）。</div>
<div>无环的&mdash;&mdash;如果你从任意的符号A开始做等价替换，你永远不会得到一个替换过A的表达式还包含A。</div>
<div>这样的等价形式总是只有唯一解。例如，当等价形式是这样的：</div>
<div>START = FIRST + SECND</div>
<div>FIRST = D + E</div>
<div>SECND = F + E</div>
<div>D = good</div>
<div>E = times</div>
<div>F = bad</div>
<div>则符号START加密了单词goodtimesbadtimes。</div>
<div>给定一个单词P，一些等式，和一个特别的符号S，请你计算S所加密的单词是否能得到P。</div></p><hr/><h3>输入格式</h3><p><p>第一行一个正整数T，表示有T组数据。每组数据第一行有一个正整数k，表示有k个等式，1 &lt;= k &lt;= 500。接下来k行，每行一个等式，等式里的字符串由空格隔开，每个字符串长度不超过5。接下来一行包含一个特殊符号S（一个大写字母组成的单词）。再接下来一行包含一个非空的由小写字母组成的单词P，P的长度不超过2000。</p>
<p></p></p><hr/><h3>输出格式</h3><p><p>对于每组数据输出一行，若能，输出&quot;YES&quot;，否则输出&quot;NO&quot;。</p></p><hr/><h3>样例输入</h3><pre>1
6
START = FIRST + SECND
FIRST = D + E
SECND = F + E
D = good
E = times
F = bad
START
debate 
</pre><hr/><h3>样例输出</h3><pre>YES
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>鸣谢Tjz</p>
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